Surface Till Geochemistry and Implications for Exploration, Black River-Matheson Area, Northeastern Ontario

Abstract The Matheson area of northeastern Ontario is of great interest for mineral exploration because of its geological similarities with the adjacent Timmins, Kirkland Lake and Larder Lake gold camps. Exploration in the area, however, is hampered by the presence of an extensive and thick cover of glacial sediments. For this reason, till geochemistry has become an important exploration method. The Ontario Geological Survey's Black River-Matheson (BRiM) reconnaissance till sampling project, carried out between 1984 and 1988, was designed to aid exploration in the Matheson area by documenting the Quaternary stratigraphy and providing a database of till geochemistry. Till samples were collected by backhoe trenching of surface pits in areas of thin drift (<5 m) and by sonic overburden drilling in areas of thicker drift. This paper summarizes the results from the shallow till sampling component of the BRiM project.
Two hundred and eighty-two surface samples were collected from Matheson Till, the youngest till sheet in the area, which was deposited during the Late Wisconsinan. For each sample, the non-magnetic heavy mineral (>3.3 S.G.) and fine (-250 mesh) till fractions were analyzed geochemically. In addition, visible gold grains were recovered by panning the heavy mineral fraction. Five areas that display multi-element anomalies in both till fractions warrant further investigation: (1) western Egan Township, overlying the Bradley Lake Syenite; (2) around and south of the Munro and Croesus mines, in Munro and Guibord townships; (3) central Garrison Township overlying the Garrison Stock; (4) south of Ore Car Lake in northern Thackeray Township; and (5) southeastern Harker Township. In these areas, Matheson Till has a local provenance and the bedrock sources for these anomalies are nearby in the up-ice (north-northwest) direction. Due to the fine-grained nature of gold in bedrock deposits in the BRiM area, the small size of most gold grains recovered from till samples (< 50 ^m) and the variable distribution of gold in the heavy mineral concentrate and fine fractions, the fine fraction in addition to the more commonly used heavy mineral concentrate should be used for gold exploration.
Surface till samples have been affected by weathering to a depth of < 3 m. Weathered till is characterized by a very low carbonate content in the matrix fraction, the absence of sulfide grains in the heavy mineral concentrate and higher concentrations of copper, nickel and zinc in the fine fraction than in the heavy mineral concentrate. As a result of the weathered/ oxidized nature of the surface till samples, the fine fraction is a better sampling medium for base metal exploration.
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Summary: The Geological Society has its own quarterly journal called Exploration
and Mining Geology, for the publication of Canadian and international papers on
applied aspects of mineral exploration and exploitation, including mineral
deposit geology, geochemistry, and geophysics, mining geology, mineral resource
appraisal and estimation methods, environmental geology, and case histories. The
editor of the journal is Jeremy P. Richards
Publication: Exploration & Mining Geology
Issue: 4
Volume: 1
Year: 1992
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Summary: During the last two decades lamproites have joined kimberlites as the only two known primary sources of economic quantities of diamonds. This paper contrasts the petrography, primary and xenocrystic mineralogy and pipe geology of these petrogenetically separate rock types. The petrographic discrimination of kimberlites and lamproites from each other, as well as other rock types found during diamond prospecting, is discussed. Kimberlites and lamproites can be classified texturally and...
Publication: Exploration & Mining Geology
Author(s): BARBARA H. SCOTT SMITH
Issue: 4
Volume: 1
Year: 1992
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Summary: The early identification of a kimberlite dyke and the occurrence of pyrope garnet grains along a section of the Munro Esker north of Kirkland Lake encouraged the search for kim-berlites. Subsequent exploration using data from aeromagnetic surveys completed for the Kirkland Lake Initiatives Program (KLIP) resulted in the discovery of five kimberlite diatremes in the area north of Kirkland Lake and another one to the south. These are only a portion of the cluster of pipes found so far that...
Publication: Exploration & Mining Geology
Author(s): J.J. BRUMMER, D.A. MacFADYEN, C.C. PEGG
Issue: 4
Volume: 1
Year: 1992
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Summary: Exploration in most areas of Canada has to contend with problems posed by glacial overburden. In many areas exploration for gold has been based on the sampling of tills, frequently by deep overburden drilling, and analyses of heavy mineral concentrates. Notwithstanding the significant role that till geochemistry has played in the discovery of some important gold deposits over the last few years, increased appreciation of the nature of the glacial history and stratisgraphy and the character of...
Publication: Exploration & Mining Geology
Author(s): IAN NICHOL, O.P. LAVIN, M.B. McCLENAGHAN, C.R. STANLEY
Issue: 4
Volume: 1
Year: 1992
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Summary: The first record of a kimberlite found in Canada (1946) was the identification of thin dykes intersected while drilling for gold in Michaud Township, Ontario.
Sampling of the Munro Esker (1964) in the Kirkland Lake area, Ontario, by the Geological Survey of Canada identified the occurrence of detrital grains of pyrope garnets along a length of 35 km of the 113 km tested. A search for the source of the garnets resulted in the identification (1968) of a narrow subsurface kimberlite dyke in the...
Publication: Exploration & Mining Geology
Author(s): J.J. BRUMMER
Issue: 4
Volume: 1
Year: 1992
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Summary: This paper documents the 1988 discovery and subsequent evaluation (to 1991) of diamond-bearing kimberlites in the Fort a la Corne area, Saskatchewan, by Uranerz Exploration and Mining Limited. Cameco Corporation began participating as a joint venture partner (50%) in mid-1989. The first indications that kimberlite-type intrusions might exist in the area came from Geological Survey of Canada aeromagnetic maps. Because of the overburden thickness (over 100 m), magnetometer surveys continue to...
Publication: Exploration & Mining Geology
Author(s): KLAUS LEHNERT-THIEL, ROLAND LOEWER, RODNEY G. ORR, PHIL ROBERT SHAW
Issue: 4
Volume: 1
Year: 1992
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Summary: The Argyle diamond mine is located in the Kimberley region in the northern part of Western Australia at approximately 16°43'S, 128°23'E in subtropical bush/shrub savannah. The 46 ha (113 acres) pipe is situated in the Halls Creek mobile zone, which was cratonized about 1800 Ma ago and adjoins the Kimberley Block, a plateau upheld by Early to Middle Proterozoic rocks underlain by presumably Archean basement. The crater and upper pipe zones of the diatreme have been preserved within tilted and...
Publication: Exploration & Mining Geology
Author(s): A.J.A. JANSE
Issue: 4
Volume: 1
Year: 1992
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